C/2023 A3 (Tsuchinshan-ATLAS)
C/2023 A3 (Tsuchinshan-ATLAS) was the great comet of October 2024, a naked-eye visitor from the distant Oort cloud. It is on a hyperbolic path — a one-way visitor that will not return. It rounded the Sun in September 2024; as of August 2026 it is roughly 8 AU from the Sun (past Jupiter) with no tail out there, and its position is CALCULATED, not tracked, as it leaves for good.
Science
Physical
- Nucleus
- A few km across (estimated)
- Composition
- A pristine nucleus of ices, dust and organics, thought to be a first-time visitor from the Oort cloud. No spacecraft has visited — its size and composition are estimated from ground-based observations.
Radiation & temperature
- Insolation
- 0.0146 S⊕ · 1% of the sunlight Earth receives
- Computed from the distance to the Sun (inverse-square; Earth's sunlight = 1), before any atmosphere.
Discovery & history
- Discovered
- January 9, 2023
- By
- Purple Mountain (Tsuchinshan) Observatory and the ATLAS survey
- Method
- Photographic plates
- Name
- Named jointly for the Tsuchinshan (Purple Mountain) Observatory in China and the ATLAS survey.
C/2023 A3 was reported by the ATLAS survey in South Africa in early 2023 and then linked to earlier images from the Tsuchinshan (Purple Mountain) Observatory in China, so it carries both names. A near-parabolic visitor from the Oort cloud, it became the great comet of October 2024, putting on a spectacular naked-eye show before receding on its long journey outward.
Images
Images from open archives · credit shown per image